if condition1 then
action1
elseif condition2 then
action2
... more elseif's if desired
else
action3
end if

The first line, second line, and last line are required ... others are optional.

A simplified form is also allowed:
If condition then expression
... no else or endif required

The syntax for iif() is:

iif(boolean condition, expressionT, expressionF)
... where a True result for the boolean (logical T/F result) condition causes the "expressionT" to be used, and a False result causes the "expressionF" to be used.

The IIF can stand alone, in a Filter Block or Color Chart, etc field that is expecting a true/false result, IF the two "expressions" themselves produce boolean logic T/F results.

Alternatively, the result of the iif() can be assigned to a dimensioned variable:
X = iif(...)

Further, iif's can be nested:

X = iif(cond1, exp1, iif(cond2, exp2, iif(cond3, exp3, exp4)))
... but BE CAREFUL with this and manually test the result ... there are certain oddball circumstances in which either the "cond" fails to parse properly, &/or the "exp" fails. I use nested IIF's quite often, but I always test them.

Finally ... none of these things are "conditional loops". The if/then/else/endif is a conditional structure with two conditional clauses. Similar terminology for IIF examples.

A "loop" is a repetitive, iterative process controlled by For/Next or Do/Until or a few other VBA syntactical options.

Further questions of this nature are best researched by googling "VBA" plus whatever your query is ... trust the Microsoft answers if available.